氟硅烷修饰的纳米复合光固化涂层提升绝缘真空闪络特性

Study on the Vacuum Flashover of Insulator with Fluorosilane Modified Nanocomposite UV Curable Coating

表面氟化被认为是提高绝缘真空沿面闪络电压的有效措施之一,然而由于材料表面形貌和元素的影响难以解耦,两者各自作用机制及抑制效果尚不清楚。为此通过在绝缘表面涂敷光固化涂层,利用涂层中氧化铝纳米片的排列堆积,构建不同粗糙度的表面形貌。进一步通过无机填料的表面氟硅烷修饰,利用固化过程的表面偏析现象在涂层表面引入氟代烃长链作为氟化层。通过闪络电压及表面电荷特性分析等表征手段,探究了表面形貌及元素组成对于介质表面耐电特性的影响。结果表明:氧化铝纳米片的排列堆积可改变表面形貌,增大粗糙度。颗粒表面偶联的氟碳链可在固化过程偏析,形成氟化层;在冲击电压作用下,粗糙的表面形貌是表面电荷积聚减少、闪络电压提高的主导因素;在高粗糙度条件下,氟化层的存在可以吸附更多能量较低的内二次电子,降低二次电子发射系数,进一步提高闪络电压。综合分析形貌及氟化层的影响后,提出了考虑体外真空侧二次电子倍增过程与体内电子输运的理论模型,该模型与表面电荷积聚特性具有良好的一致性。

Surface fluorination is regarded as an effective means for the enhancement of vacuum flashover strength. However, due to the changes of surface roughness and different chemical compositions, their separate influence and corresponding mechanism are still unclear. Consequently, UV-cured nanocomposite coating was sprayed onto the surface of polymeric insulation. Rougher morphology was formed by nano-Al2 O3 flakes in the coating layer. Furthermore, a fluorination layer could be gained by fluorosilane treatment of Al2 O3 flakes due to surface segregation in UV curing process. The influence of surface morphology and surface fluorinated chains on the surface flashover strength and charge behaviors in vacuum were investigated systematically. Experimental results reveal that the morphology will change and the surface roughness of the coating layer will gradually increase as nano-Al2 O3 flakes pile up, and the fluorinated chains are segregated to the surface. Surface morphology is the domain factor for the enhanced pulsed flashover strength and surface charging mitigation. Experiments indicate that the presence of fluorination layer traps more internal secondary electrons with low energy in the case of high roughness level, thereby further improving flashover strength. A theoretical model considering outside secondary electron multipactor and inside electron transport was proposed, which is in good agreement with surface charging characteristics.